/proc/softirqs provides counts of softirq handlers serviced since boot time, for each CPU.
cat /proc/softirqs CPU0 CPU1 CPU2 CPU3 HI: 0 0 0 0 TIMER: 27166 27120 27097 27034 NET_TX: 0 0 0 17 NET_RX: 42 0 0 39 BLOCK: 0 0 107 1121 TASKLET: 0 0 0 290 SCHED: 27035 26983 26971 26746 HRTIMER: 0 0 0 0 RCU: 1678 1769 2178 2250